1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device and more particularly to an LCD device having an improved image-display region.
2. Discussion of the Related Art
The LCD device, which uses optical anisotropy and polarization properties to display an image, is widely used for notebook computers, monitors, TV, and so on, because of its high contrast ratio and characteristics adequate to display moving images.
The LCD device includes a liquid crystal panel having a first substrate, a second substrate and a liquid crystal layer. The first and second substrates face each other, and the liquid crystal layer is interposed therebetween. An arrangement of the liquid crystal molecules in the liquid crystal layer is changed by an electric field induced in the liquid crystal panel to control light transmissivity.
Generally, an additional light source is required because the LCD panel is a non-emissive-type display device. Accordingly, a backlight unit is disposed under the LCD panel. The LCD device displays images using light produced by the backlight unit and supplied to the LCD panel.
The backlight unit may include a cold cathode fluorescent lamp (CCFL), an external electrode fluorescent lamp or a light emitting diode (LED) as a light source. Among these light sources, the LED is widely used because it has advantages in size, power consumption, reliability and so on.
FIG. 1 is a cross-sectional view of the related art LCD device. In FIG. 1, the LCD device includes a liquid crystal panel 10, a backlight unit 20, a main frame 30, a top frame 40 and a bottom frame 50.
The liquid crystal panel 10 includes a first substrate 12, a second substrate 14 and a liquid crystal layer (not shown). The first and second substrates 12 and 14 face each other, and the liquid crystal layer is interposed therebetween. First and second polarization plates (not shown) are disposed on opposite sides of the liquid crystal panel 10.
The backlight unit 20 is disposed under the liquid crystal panel 10 to provide light toward the light crystal panel 10. The backlight unit 20 includes an LED assembly 29, a reflective sheet 25, a light guide plate 21 and an optical sheet 23. The LED assembly 29 is arranged along at least one side of the main frame 30. The reflective sheet 25 is disposed on the bottom frame 50 and has a color of white or silver. The light guide plate 21 is disposed on the reflective sheet 25, and the optical sheet 23 is disposed on or over the light guide plate 21.
The LED assembly 29 is disposed at a side of the light guide plate 21 and includes an LED printed circuit board (PCB) 27 and an LED 28 arranged on the LED PCB 27.
The liquid crystal display panel 10 and the backlight unit 20 are combined using the main frame 30 that can prevent movement of the liquid crystal panel 10 and the backlight unit 20. The top frame 40 cover edges of the liquid crystal panel 10 and sides of the main frame 30, so the top frame 40 can support and protect of the edges of the liquid crystal panel 10 and sides of the main frame 30. The bottom frame 50 covers back edges of the main frame 30, so the bottom frame 50 is combined with the main frame 30 and the top frame 40 for modularization.
A position of the elements of the backlight unit 20, e.g., the light guide plate 21 and the optical sheet 23 is fixed by the main frame 30. In addition, the main frame 30 guides the liquid crystal panel 10.
On the other hand, minimization of a bezel, where an image is not displayed because of the LED assembly 29, the main frame 30, the top frame 40, is preferable. Namely, an LCD device including smaller bezel and larger image-display region is preferable. This LCD device may be referred to as a narrow bezel structure LCD device.
To meet this preference, an end of the main frame 30 and an end of the display region are matched to increase the image-display region.
However, in this instance, the light from the LED assembly 29 is directly incident to the liquid crystal panel 10 without passing through the light guide plate 21 and the optical sheet 23 such that problems, e.g., brightness line defect and hot spots, are generated. To avoid these problems, a light-shielding element such as a light-shielding film is attached onto a top edge of the light guide plate 21 or a bottom edge of the liquid crystal panel 10.
Unfortunately, there are disadvantages in production costs and production yield and limitations for the narrow bezel structure.